The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs.
For example, as optical lithography approaches its technological and economical limits, a directed self-assembly (DSA) process emerges as a potential candidate for patterning dense features. A DSA process takes advantage of the self-assembling properties of materials, such as block copolymers, to reach nanoscale dimensions while meeting the constraints of current manufacturing. Typical DSA processes require a guide pattern that “guides” the self-assembling process. The uniformity and precision of the guide pattern largely affect the quality of the self-assembled polymer features, as well as the final pattern density. Therefore, a guide pattern with precise critical dimension (CD) is desired.